A power transmitting apparatus for transmitting the vehicle engine power, such as an automobile to the vehicle wheels, is required not only to transmit the engine power to the wheels but to enable radial and axial displacements and a moment displacement of the wheels caused by bounce of the wheel or turning of the vehicle during running on a rough road. Accordingly as shown in FIG. 18, an engine side (e.g. a transmission) and a wheel are connected via a drive shaft 100. One end is connected to a differential apparatus 102, via a slide type constant velocity universal joint 101, and the other end is connected to a wheel 105, via a wheel bearing apparatus 104 that includes a secured type constant velocity universal joint 103.
The wheel bearing apparatus 104 is a so-called “third generation” type wheel bearing 106. The secured type constant velocity universal joint 103 is detachably connected to the wheel bearing apparatus 106. In recent years, there has been a tendency to shift from the third generation structure to a so-called “fourth generation” structure. Here, the wheel bearing 106 and the secured type constant velocity universal joint 103 are combined as a unit.
In an axle module of a wheel bearing apparatus of the fourth generation, a constant velocity universal joint forms part of the wheel bearing apparatus. A drive shaft is connected to a pair of constant velocity universal joints, including the above constant velocity universal joints, and are combined as a unit. It is further know to combine a cover unit to improve the workability of the assembly of the axle module onto a vehicle as well as to protect a boots of the constant velocity universal joint during assembly and transportation of the axle module. As shown in FIG. 19, an axle module is formed by a wheel bearing apparatus that includes an outer member 50 formed with a body mounting flange 50b on its outer circumferential surface. The flange 50b is adapted to be mounted on a knuckle “N”. A fitting surface 50c is inserted into the knuckle “N”. Double row outer raceway surfaces 50a, 50a are on the outer member inner circumferential surface. An inner member 55, including a wheel hub 53, is inserted into the outer member 50 via double row balls 51, 51. The inner member 55 is integrally formed with a wheel mounting flange 52 on one end. Its outer circumferential surface has one inner raceway surface 53a opposite to one of the double row outer raceway surfaces 50a, 50a. An outer joint member 54 is formed with another inner raceway surface 54a on its outer circumferential surface. The inner raceway surface is opposite to the other one of the double row outer raceway surfaces 50a, 50a. A joint assembly “JA” is connected to the wheel bearing apparatus. In addition the outer diameter of the fitting surface 50c is formed larger than the maximum outer diameter of the constant velocity universal joint. An elastomeric cover unit 57 is formed as a cylindrical member to cover the periphery of the joint assembly “JA”. The cover unit 57 is formed with contracted portions 57a, 57a at its opposite ends. The joint assembly “JA” has a pair of constant velocity universal joints 56, 58 and a drive shaft 59 connecting the two constant velocity universal joints 56, 58.
The cover unit 57 covers the periphery of the joint assembly “JA” and protects the joint assembly “JA” to make handling, such as transportation, easy. In addition, the elastic contracted portions 57a, 57b on the cover unit 57 enable easy mounting in a “one-touch” manner” of the cover unit 57 onto the outer joint member 54 of the constant velocity universal joint 56. Also, it prevents the cover unit 57 from falling out (see Japanese Laid-open Patent Publication No. 256938/2005).